Method and Apparatus for Cooperative Positioning in a Wireless Communication Network

ABSTRACT

According to the teachings herein, a wireless device that is a candidate for operating in the cooperative positioning advantageously activates that mode in response to detecting a warning situation. In some embodiments, the detection and/or activation operations are autonomously undertaken by the wireless device. In other embodiments, the wireless communication network provides warning situation detection and/or control of the cooperative positioning mode. More generally, the wireless communication network maintains a database identifying those wireless devices within a given service area that are cooperative positioning mode candidates—e.g., the devices having D2D communication capability and operational configurations that allow such operation. By the network providing such information in advance of a warning situation, the candidate devices have the information needed to efficiently discover or otherwise identify other such candidates.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/442,545, filed 13 May 2015, which is a U.S. National PhaseApplication of PCT/SE2013/050338 filed 26 Mar. 2013. The entire contentsof each of the aforementioned applications are incorporated herein byreference.

TECHNICAL FIELD

The present invention generally relates to wireless communicationnetworks, and particularly relates to cooperative positioning in suchnetworks.

BACKGROUND

Public Land Mobile Networks (PLMNs) represent one example of the typesof communication networks that can and do play a valuable role in publicsafety and information dissemination. For example, Release 8 of theThird Generation Partnership Project (3GPP) specifications provides forwireless system parts and associated system protocols referred to as the“Earthquake and Tsunami Warning System” or ETWS. The ETWS addresses anumber of disaster situations and operates with the goal of collectingseismic sensor or other threat information and relaying to emergencypoints or other alert system nodes, for distribution to wirelessdevices. Release 9 included provisions for a Commercial Mobile AlertSystem (CMAS), which is designed to distribute alert signals to cellularusers operating within the coverage area(s) of a cellular system.Further, the reader may refer to the 3GPP document “TechnicalSpecification TS 22.268,” for details regarding the current state of theart for the 3GPP Public Warning System.

However, in a disaster or other type of national security or publicsafety (NSPS) situation, all or part of the cellular and local wirelessnetwork infrastructure may be impaired, e.g., may become damaged orotherwise become dysfunctional. Such infrastructure impairment degradesor eliminates communication services, at least within the affectedareas. Further, the impairment of network infrastructure can result inunreliable and/or imprecise operation of the cellular location services(LCS) broadly relied upon for determining the geographic position ofwireless devices operating within the network. The degradation oroutright loss of reliable, accurate device positioning in NSPSsituations has serious, potentially lethal consequences.

An example of such a situation is when a user equipment or “UE” losescellular and wireless local network coverage and it does not have itsown mechanism for determining its location, or is operating in anenclosed space or other environment where its onboard positioning systemoperates poorly or not at all. Device-based location mechanisms includeGlobal Navigation Satellite System (GNSS) circuits, such as a GlobalPositioning System (GPS) circuitry, Galileo-based circuitry, etc. Suchsystems may use network assistance, e.g., Assisted GNSS (A-GNSS) andthus are vulnerable to a loss of assistance data arising from impairmentof the network infrastructure, or arising from movement of the deviceinto a location that prevents the reliable reception of the assistancedata.

The impairment of network-provided and/or network-assisted positioning,broadly referred to as “infrastructure based positioning” to denote thereliance on the network for device positioning, at best leaves thedevice owner or operator with an unreliable estimate of the device'sposition. At worst, the device owner or operator is left without anypositioning information. Here, the phrase “device owner or operator”denotes any person, machine or system that uses or includes a wirelesscommunication device for communication network services, including LCS.Non-limiting examples of such devices include feature phones,smartphones, machine type communication devices or machine-to-machine(M2M) communication devices, target devices, embedded or integrateddevices, USB-dongles, network modems or other wireless adaptors,in-vehicle communication modules, etc.

Further, there are many types and/or variations of “infrastructure basedpositioning.” One example is the aforementioned A-GNSS approach. Otherexamples include Observed Time Difference of Arrival (OTDOA) positioningmethods, Uplink Time Difference of Arrival (UTDOA) positioning methods,enhanced Cell ID (E-CID) based positioning methods, and various hybridmethods, such as a combination of A-GNSS and OTDOA-based measurements.These techniques implicate any number of network infrastructure entitiesbeyond the base stations and their backhaul and side-haul links, such asLocation Measurement Units (LMUs) serving as measurement nodes foruplink signals from wireless devices operating within the network, or,in the case of Long Term Evolution (LTE) networks, one or more EnhancedServing Mobile Location Centers (E-SMLCs).

Against this backdrop, the 3GPP SA1 working group is studying thefeasibility of Proximity Services (ProSe) for national security andpublic safety use cases. Refer, for example, to the technical report,3GPP TR 22.803 “Proximity Services (ProSe)”. Such proximity services canbe provided by direct device-to-device (D2D) communications, in whichtwo or more devices communicate via a direct communication link, ratherthan communicating through a cellular base station (BS) or a wirelesslocal area network (WLAN) access point (AP) or a relay. In the LTEcontext, this type of communication is referred to as “LTE Direct.”

Because D2D communications utilizing LTE Direct or some other ad hocnetworking technology, such as Bluetooth or WiFi Direct, can take placeeven with limited or no infrastructure support, it is identified as animportant technology enabler for ProSe in a catastrophe or otheremergency situations.

However, peer-to-peer cooperative positioning methods, in which peerwireless devices exchange positioning information to determine and/orrefine their respective positioning determinations, generally still relyon the availability of cellular or WLAN access points with respect to atleast some of the peer devices involved in cooperative positioning. Forexample, wireless devices operating in a GNSS-hostile environment (e.g.,indoors) or devices without GNSS capability receive peer positioninginformation from one or more other wireless devices that know theirabsolute positions as a consequence of network-assisted ornetwork-performed positioning. LTE Direct or other D2D communicationwithin the cellular network radio spectrum may be used for D2Dcommunications, for peer-based device positioning, communication withproximate first responders, etc.

Known approaches to implementing D2D communications consider radioresource availability, network load, radio propagation conditions, andother physical and lower-layer parameters. In general, the currentalgorithms used for activating D2D communications tend to select devicesfor D2D communications based on minimizing the interference caused bysuch devices, which results in the selection of devices that are moredistant from the cellular base stations and/or other wireless accesspoints. However, it is recognized herein that such approaches do notconsider the various degradations in infrastructure positioning accuracyand reliability that may occur with even a partial impairment of networkinfrastructure.

SUMMARY

According to the teachings herein, a wireless device that is a candidatefor operating in the cooperative positioning advantageously activatesthat mode in response to detecting a warning situation. In someembodiments, the detection and/or activation operations are autonomouslyundertaken by the wireless device. In other embodiments, the wirelesscommunication network provides warning situation detection and/orcontrol of the cooperative positioning mode. In at least one embodiment,the wireless communication network maintains a database identifyingthose wireless devices within a given service area that are cooperativepositioning mode candidates. By the network providing such informationin advance of a warning situation, the candidate devices have theinformation needed to efficiently discover or otherwise identify othersuch candidates.

In an example implementation, a network node, such as a base station ora positioning node in a wireless communication network, is configured tocarry out a method that includes detecting a warning situation that isassociated with actual or expected impaired operation of the wirelesscommunication network. The warning situation will be understood asapplying to one or more service areas of the network and the methodfurther includes identifying wireless devices in the service area(s)that are candidates for operating in a cooperative positioning mode, forperforming device positioning, and sending a message to the identifiedwireless devices, to activate the cooperative positioning mode.

For example, the message indicates the warning situation and thewireless devices autonomously activate the cooperative positioning moderesponsive to the indication, or the message includes an explicitcommand to activate the cooperative positioning mode. The network nodealso may be configured to “bootstrap” the activation of cooperativepositioning mode by the candidate wireless devices, based ontransmitting signaling that identifies those devices within the servicearea(s) that are candidates for operating in the cooperativepositioning. By having this information in advance of an actual orexpected warning situation, a given candidate device can more easilydiscover or otherwise identify neighboring candidate devices, once itactivates the cooperative positioning mode.

Regarding device-side aspects of the teachings herein, an examplewireless device is configured to perform a method that includesdetecting a warning situation that is associated with actual or expectedimpaired operation of the wireless communication network within acurrent service area of the wireless device, and activating acooperative positioning mode that relies on exchanging positioninginformation with other wireless devices using D2D communications. Theexample method further includes detecting one or more other wirelessdevices in the service area that are candidates for engaging incooperative positioning with the wireless device, performing cooperativepositioning in conjunction with one or more of the detected wirelessdevices. As noted earlier, the detecting step may be aided or otherwisebootstrapped by information received from the wireless communicationnetwork in advance of the warning situation, where such informationidentifies the other devices within the service area that are candidatesfor operating in the cooperative positioning mode.

Of course, the present invention is not limited to the above featuresand advantages. Indeed, those skilled in the art will recognizeadditional features and advantages upon reading the following detaileddescription, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of one embodiment of a wireless communicationnetwork that includes one or more nodes configured according to theteachings herein.

FIG. 2 is a block diagram of one embodiment of a radio base station,such as may be used in the wireless communication network introduced inFIG. 1.

FIG. 3 is a logic flow diagram of one embodiment of a method ofprocessing as taught herein for a network node.

FIG. 4 is a diagram of example signaling and information exchanges, suchas may be used in one or more embodiments of the teachings herein.

FIG. 5 is a block diagram of one embodiment of a wireless device, suchas may be used in the wireless communication network introduced in FIG.1.

FIG. 6 is a logic flow diagram of one embodiment of a method ofprocessing as taught herein for a wireless device.

DETAILED DESCRIPTION

FIG. 1 illustrates one embodiment of a wireless communication network10, including a Radio Access Network (RAN) portion 12 and a Core Network(CN) portion 14 that communicatively couples with one or more externalnetworks 16. While not the only contemplated mechanism for detectingactual or impending warning situations, it will be understood thatEmergency Threat Warning System (ETWS) messages and/or other warninginformation may be received via the external networks 16.

The RAN 12 includes one or more cells 18 and corresponding base stations20 that provide communication services in those cells 18—these cells 18or combinations of them may be more generally referred to as “serviceareas 18.” Where suffixing aids clarity, the service areas 18 may bereferred to as service area 18-1, 18-2, and so on. Likewise, if neededfor clarity, the base stations 20 may be referred to as base station20-1, 20-2, and so on. Each base station 20 supports communicationservices for wireless devices 22 operating in the service area(s) 18associated with that base station 20. Where needed for clarity,individual wireless devices 22 may be referred to as wireless device22-1, 22-2, and so on.

One also sees that the CN 14 includes a few example nodes, such as aMobility Management Entity (MME) 24, a Serving Gateway (SGW) 26, and apositioning node 28. In an LTE-based embodiment of the network 10, thepositioning node 28 may be an Enhanced Serving Mobile Location Center orE-SMLC. In that case, the E-SMLC is connected to an LTE base station(i.e., eNode B) via an interface which uses LTE positioning protocolannex (LPPa). The E-SMLC communicates with a wireless device 22 directlyvia LTE positioning protocol annex (LPP), which is transparent to LTEbase stations, including the serving base station 20 of the wirelessdevice 22.

FIG. 2 illustrates a base station 20 as one non-limiting example of thetype of network node that may be configured to support the network-sideteachings herein. The illustrated base station 20 includes acommunication interface 30, e.g., for communicating with wirelessdevices 22 using radio resources. The base station 20 further includesprocessing and control circuits 32, which include a positioningprocessing circuit 34 and include or are associated with one or morestorage elements 36 that store, e.g., database information 38 and/or acomputer program 40. The base station 20 further includes one or moreadditional communication interfaces 42, e.g., for communication with theCN 14 and/or with other base stations 20.

In more detail, in one or more embodiments, the communication interface30 is configured for sending signals to wireless devices 22 andreceiving signals from wireless devices 22, and the positioningprocessing circuit 34 is operatively associated with the communicationinterface 30. The positioning processing circuit 34 is not necessarilyconfigured to perform actual positioning calculations for wirelessdevices 22. Instead, it is referred to a “positioning” related circuitbecause it is configured to support activation of the cooperativepositioning mode by given wireless devices 22, according to theteachings herein. For brevity, it is referred to hereafter as the“processing circuit 34.”

In an example configuration, the processing circuit 34 is configured todetect a warning situation that is associated with actual or expectedimpaired operation of the wireless communication network 10 within aservice area 18, identify wireless devices 22 in the service area 18that are candidates for operating in a cooperative positioning mode forperforming device positioning, and sending a message to the identifiedwireless devices 22, to activate the cooperative positioning mode. Asnoted, the cooperative positioning mode relies on exchanging positioninginformation between respective wireless devices 22 using D2Dcommunications. Thus, cooperative positioning mode operation offersdistinct advantages in reliability and/or accuracy as compared to use ofan infrastructure-based positioning mode which may not work well, orwork at all, in the presence of network impairment.

FIG. 3 illustrates an embodiment of a method 300 that corresponds to theabove-described processing for the base station 20. However, it will beappreciated that this functionality can be implemented at other types ofnetwork nodes, e.g., adapted for operation in one or more CN nodes, orone or more dedicated nodes may be added to carry out suchfunctionality, e.g., based on propagating signaling toward the wirelessdevices 22 via the base stations 20.

In one example, the network node in question can be a positioning nodesuch as E-SMLC in LTE, which is configured for operation in a wirelesscommunication network (10). During such operation, the example E-SMLCdetects a warning situation, identifies wireless devices (22) in aservice area (18) that are candidates for operating in a cooperativepositioning node for performing device positioning and sends a messageto the identified wireless devices (22), to activate the cooperativepositioning mode. The positioning node may detect the warning situationfor example based on information received from a wireless device or anyother node, e.g. a MME, or a warning content provider, etc. Thepositioning node may identify the wireless devices (22) that arecandidates for operating in a cooperative positioning mode based on atleast one of: received information from the wireless devices, historicaldata regarding wireless devices (22) that have operated in a cooperativepositioning mode, or information received from another node, e.g. a MME,a serving base station, etc.

With these implementation variations in mind, the method 300 accordingto the illustrated example includes detecting (Block 302) a warningsituation that is associated with actual or expected impaired operationof the wireless communication network 10, at least within a service area18; identifying (Block 304) wireless devices 22 in the service area 18that are candidates for operating in a cooperative positioning mode forperforming device positioning, wherein the cooperative positioning moderelies on exchanging positioning information between respective wirelessdevices 22 using D2D communications; and sending (Block 306) a messageto the identified wireless devices 22, to activate the cooperativepositioning mode.

A few points regarding the method 300 will be helpful in understandingits operation and potential for variation without departing from theessence of these teachings. First, one or more of the illustrated methodsteps may be performed in a different order, or may be performed inparallel, or in a loop, and/or on an ongoing, background or continuingbasis. For example, identifying the wireless devices 22 within a givenservice area 18 that are candidates for operating in the cooperativepositioning mode may be an ongoing process. For example, with respect toany given wireless device 22, the network node may determine whether itis or is not a candidate for operating in the cooperative positioningmode as part of admission control, device registration, call setup, etc.

Also, the particular details of one or more of the illustrated methodsteps may depend on the nature of the wireless devices 22 at issue. Forexample, sending (Block 306) the message may comprise sending a warningsituation indicator to the identified wireless devices 22, at least incases where the identified wireless devices 22 are configured toautonomously activate the cooperative positioning mode responsive toreceiving the warning situation indicator. Additionally, oralternatively, the sending step comprises sending an explicit command tothe identified wireless devices 22, commanding the identified wirelessdevices 22 to activate the cooperative positioning mode. In at least oneexample, sending (Block 306) the message comprises sending a modeswitching command to the identified wireless devices 22, commanding theidentified wireless devices 22 to switch from the infrastructurepositioning mode to the cooperative positioning mode in response to themode switching command.

In other variations, the step of identifying (Block 304) the wirelessdevices 22 in the service area 18 that are candidates for operating inthe cooperative positioning mode may be based on any one or moredeterminations. In one example, identifying which wireless devices 22are candidates for operating in the cooperative positioning modecomprises determining which ones of them have D2D communicationscapability. However, while D2D communications capability is arequirement for cooperative positioning, a given wireless device 22 mayhave D2D communications capability and yet be unable to operate in thecooperative positioning mode.

For example, a wireless device 22 may support D2D communications but notsupport cooperative positioning. Thus, in an example embodiment,determining whether a wireless device 22 is a candidate comprisesdetermining that the wireless device 22 is capable of operating in thecooperative positioning mode. This determination comprises, for example,receiving or otherwise inspecting device capability information thatexplicitly or implicitly indicates that the wireless device 22 at leasthas the capability of operating in the cooperative positioningmode—e.g., some baseline cooperative positioning capability. Suchcapability information can be indicated in conjunction with orseparately from an indication of D2D communication capability. Further,such capability information may indicate particular configurationsand/or limitations regarding the device's cooperative positioningcapabilities and identifying the wireless device 22 as being a candidatemay depend on assessing the particular configuration or capabilitydetails.

In another variation, it is recognized herein that a given wirelessdevice 22 is not necessarily a candidate for operating in thecooperative positioning mode even when it is known that the wirelessdevice 22 is capable of cooperative positioning. As an example, at leastwhere permitted by law, the device owner may be permitted to disable orotherwise disallow the wireless device 22 to perform cooperativepositioning, e.g., out of concerns for personal privacy, battery life,etc. Thus, in at least some embodiments, determining whether a givenwireless device 22 is a candidate for operating in the cooperativepositioning mode comprises determining whether the wireless device 22has an operational configuration that permits such operation. To thisend, configuration information received from/for the wireless device 22may include, e.g., a flag, an information element, or some other form ofindicator that indicates that cooperative positioning operation ispermitted.

Any one or more of such candidacy determinations are based on, forexample, the network node receiving capability information from wirelessdevices 22 at call setup and/or at other times. In a minimal case, thecapability information received for an individual wireless device 22indicates whether or not that device is capable of D2D communications.Additionally, or alternatively, the capability information indicateswhether the wireless device 22 has cooperative positioning capability.Still further, the network node may determine candidacy based onreceiving information indicating that the wireless device 22 ispermitted to operate in a cooperative positioning mode.

Broadly, it is recognized herein to use information received from, orotherwise known for, given wireless devices 22, to determine which onesof those wireless devices 22 should be considered as candidates foroperating in a cooperative positioning mode. At least some suchinformation may be known based on the network node receiving capabilityand/or operational configuration information from such wireless devices22, or from another network node such as a core network node (e.g., anMME) or a serving base station. For example, for a given wireless device22, the network node may evaluate capability information that indicatesD2D and/or cooperative positioning capabilities of the device. Thedevice may be deemed a candidate or not on that basis. However, thenetwork node may also evaluate operational configuration information.Consider the case where the capability information indicates that thedevice has the capability of operating in a cooperative positioningmode, but operational configuration information for the device indicatesthat cooperative positioning is not permitted. In this case, the networknode would not deem the device as a candidate. Such indications may beexplicit or implicit.

With these points of flexibility in mind, the network node identifiesthe wireless devices 22 in a service area 18 that are candidates foroperating in a cooperative positioning mode by determining whichwireless devices 22 in the service area 18 at least have D2Dcommunications capability. This candidacy determination may include, ormay be extended, by the network node determining which wireless devices22 at least have the capability of supporting cooperative positioning.Still further, the candidacy determination may include, or may beextended, by the network node determining which wireless devices 22 arepermitted or willing to operate in the cooperative positioning mode.Thus, there may be a set of devices having D2D capability, a potentiallysmaller set of devices having D2D and cooperative positioningcapabilities, and potentially smaller set of devices having D2D andcooperative positioning capabilities and further having operationalconfigurations that permit cooperative positioning. Any and all suchdeterminations may be based on the network node receiving capabilityinformation and/or operational configuration information for individualones of the wireless devices 22 in the service area 18.

Turning to other aspects of the method 300, it will be appreciated thatthe wireless communication network 10 uses certain radio resources forcommunicating with wireless devices 22. Correspondingly, the method 300may include the base stations 20 or other network nodes reserving aportion of the radio resources, for use in cooperative positioning usingD2D communications. In other words, the network 10 may advantageouslyset aside a portion of its radio resources, for use in cooperativepositioning operations. As such, the method 300 in one or moreembodiments also includes the base stations 20 or other network nodesindicating the reserved portion of the radio resources to the identifiedwireless devices 22, either in advance of or in conjunction with sendingthe message. The indication may be sent to all wireless devices 22,e.g., via general broadcast, or may be sent only to those wirelessdevices 22 identified as candidates for operating in the cooperativepositioning mode.

In another example of the variations and extensions of the method 300contemplated herein, the method 300 may include sending (Block 306) themessage as a warning situation severity indicator—e.g., a value takenfrom a severity scale or a value that indicates a particular type ofwarning situation. Examples of severity scale values are no warning, lowwarning, medium warning and high warning, which can be expressed usingtwo bits of information. Examples of particular types of warningsituations are fire, earthquake, flood, etc. A particular type ofwarning situation may represent an on-going event (e.g., fire) or anexpected event (e.g., Tsunami). In one of the advantageous correspondingconfigurations contemplated for wireless devices 22, the wirelessdevices 22 are configured to decide whether or not to activate thecooperative positioning mode in dependence on the severity of thewarning situation, as indicated by the warning situation severityindicator.

Still further, in at least some embodiments, the method 300 furtherincludes sending signaling indicating the identified wireless devices22—i.e., identifying the wireless devices 22 that have been identifiedas candidates for operating in the cooperative positioning mode. Suchinformation is sent generally to all wireless devices 22 within theservice area(s) 18, or is sent only to the identified wireless devices22. In either case, it will be understood that such information is foruse by individual ones of the identified wireless devices 22 indiscovering other ones of the identified wireless devices 22, forengaging in cooperative positioning. For example, such information mayinclude device identifiers, radio beacon information, etc., or othersuch information that will aid a given candidate wireless device 22 infinding other candidate wireless devices 22 that are proximate to it.

FIG. 4 illustrates a non-limiting example of such signaling. Here, onesees a generalized service area 80 and an associated network entity(NWE) 82 operating as an example of the base station 20 or other networknode contemplated herein. The NWE 82 obtains a number of informationitems during, e.g., device registration, such as D2D capabilityinformation, positioning capability information, cooperative positioningcapability information, willingness to participate in cooperativepositioning, etc. The NWE 82 also broadcasts or otherwise transmitsassistance information, e.g., as needed or on a periodic basis. Thisinformation includes, for example, an identification of the radioresources to be used by the wireless devices 22 for cooperativepositioning, e.g., OFDM resource block reservations, time slots,subframes, maximum allowed transmit power, transport format (e.g.,modulation and coding scheme) of data blocks used for transmission,multi-antenna transmission modes (e.g., transmit diversity),multi-antenna reception modes (e.g., receiver diversity, etc.)—which canhelp greatly in reducing the cooperative positioning signal search spacefor wireless devices 22 in an emergency. The NWE 82 also may provideother information, e.g., the maximum transmit power to be used incooperative positioning, the cooperative positioning algorithm(s) thatshould be used, and the IDs of other wireless devices 22 that will orare expected to be available for cooperative positioning.

Now, with respect to the method 300, it will be appreciated that theillustrated base station 20 or other network node may be configured tocarry out the method 300 based on the execution of computer programinstructions. That is, the processing circuit 34 may be speciallyadapted to carry out the method 300, based at least in part on itsexecution of a computer program product recorded in a computer readablestorage medium, such as the storage elements 36, which may comprise oneor more memory circuits, such as FLASH, EEPROM or other non-volatilestorage, along with SRAM, DRAM, or other working memory.

In one example, the computer program 40 shown by way of example in FIG.3 comprises computer program instructions that, when executed by theprocessing circuit 34 to detect a warning situation that is associatedwith actual or expected impaired operation of the wireless communicationnetwork 10 within a service area 18; identify wireless devices 22 in theservice area 18 that are candidates for operating in a cooperativepositioning mode for performing device positioning; and send a messageto the identified wireless devices 22, to activate the cooperativepositioning mode.

FIG. 5 provides an example of device-side configuration details, whereina wireless device 22 comprises one or more transmit/receive (TX/RX)antennas 50, for transmitting uplink (UL) signals to the wirelesscommunication network 10, and for receiving downlink (DL) signals fromthe wireless communication network 10. Further, the example wirelessdevice 22 includes antenna interface circuitry 52 coupling the antennas50 with transmitter circuitry 54 and with a receiver front-end 56. Thetransmitter circuitry 54 includes, for example, at least the poweramplifier (PA) circuitry and associated frequency controls needed fortransmitting communication signals at the desired frequencies. Suchcircuitry may be driven by and controlled by baseband processingcircuits, generally represented as processing and control circuits 60.

Similarly, the receiver front-end circuits 56 may be controlled by theprocessing and control circuits 60, which may comprise one moremicroprocessors, microcontrollers, DSPs, ASICs, FPGAs, or other suchdigital processing circuitry. In an example case, the receiver front-end56 includes filters, gain control circuitry, low-noise amplifiers, anddown-conversion/digitization circuitry, as needed, to obtaintime-varying streams of digital sample values corresponding to one ormore antenna-received DL signals.

The processing and control circuits 60 at least functionally include apositioning processing circuit 62 and further includes or is associatedwith one or more storage elements 64, storing configuration data 66and/or a computer program 68. Depending upon its sophistication andintended usage, the wireless device 22 may include any number ofadditional processing circuits 70 and/or interface circuitry 72—e.g.,sensor interfaces, keypads, display screens, and/or other input/outputcircuits.

In more detail, in an example configuration, the antennas 50, antennainterface circuitry 52, transmitter circuitry 54 and receiver front-end56 operate as a communication interface that is configured for sendingsignaling to and receiving signaling from the wireless communicationnetwork 10, and the positioning processing circuit 62 is operativelyassociated with the communication interface and is configured to: detecta warning situation that is associated with actual or expected impairedoperation of the wireless communication network 10 within a currentservice area 18 of the wireless device 22; activate a cooperativepositioning mode that relies on exchanging positioning information withother wireless devices 22 using D2D communications; detect one or moreother wireless devices 22 in the service area 18 that are candidates forengaging in cooperative positioning with the wireless device 22; andperform cooperative positioning in conjunction with one or more of thedetected wireless devices 22.

In at least one such embodiment, the one or more storage elements 64store the computer program 68 as a computer program product recorded ina computer readable storage medium. The program 68 comprises computerprogram instructions that, when executed by the processing circuit 62,configure the wireless device 22 to perform the above-specifiedoperations. As such, the processing circuit 62 can be understood asbeing specially adapted to carry out the device-side aspects of theteachings herein, based at least in part on its execution of storedcomputer program instructions.

More broadly, whether realized through the programmatic configuration ofthe processing circuit 62, or realized through fixed circuitry, or somecombination of both, the example wireless device 22 is configured tocarry out a method 600. In the illustrated example of FIG. 6, the method600 includes: detecting (Block 602) a warning situation that isassociated with actual or expected impaired operation of the wirelesscommunication network 10 within a current service area 18 of thewireless device 22; activating (Block 604) a cooperative positioningmode that relies on exchanging positioning information with otherwireless devices 22 using D2D communications; detecting (Block 606) oneor more other wireless devices 22 in the service area 18 that arecandidates for engaging in cooperative positioning with the wirelessdevice 22; and performing (Block 608) cooperative positioning inconjunction with one or more of the detected wireless devices 22.

In one example, the method 600 includes the wireless device 22 receivinginformation from the wireless communication network 10 that identifiesthe candidate wireless devices 22. Here, the step of detecting in Block606 comprises the wireless device 22 using the received information fordiscovering or otherwise identifying one or more of the candidatewireless devices 22. For example, it receives device IDs for thecandidate wireless devices 22 and uses those IDs to detect beaconsignals (aka broadcast signals, pilot signals, identifying signals,etc.) from such other devices. In support of such functionality, in oneor more embodiments, the wireless device 22 sends information to thewireless communication network 10 that indicates that the wirelessdevice 22 is a candidate for operating in the cooperative positioningmode.

In one such example, the method 600 also may include the wireless device22 sending information to the wireless communication network 10 thatindicates that the wireless device 22 is a candidate for operating inthe cooperative positioning mode, where that sending operation comprisesat least one of: sending information to the wireless communicationnetwork 10 that indicates that the wireless device 22 is a candidate foroperating in the cooperative positioning mode comprises at least one of:sending information indicating that the wireless device 22 is at leastcapable of using D2D communications; sending information indicating thatthe wireless device 22 is at least capable of supporting cooperativepositioning; and sending information indicating that the wireless device22 is permitted or willing to perform cooperative positioning.

In other variations, the detecting operation in Block 602 comprises thewireless device 22 receiving a message from the wireless communicationnetwork 10 that includes a warning situation indicator. In this examplecase, the wireless device 22 is configured to perform the activationstep in Block 604 autonomously—i.e., it activates the cooperativepositioning mode in response to receiving the warning situationindicator.

In an alternative configuration, the detecting operation in Block 602comprises receiving a message from the wireless communication network 10that includes a command to activate the cooperative positioning mode.Here, the wireless device 22 is configured to activate the cooperativepositioning mode in response to the command.

For example, detecting (Block 602) the warning situation comprises thewireless device 22 receiving a mode switching command from the wirelesscommunication network 10, and switching from the infrastructurepositioning mode to the cooperative positioning mode in response to themode switching command. The warning may be, for example, any of: amessage or command to activate D2D cooperative positioning; a message orcommand to abandon infrastructure based positioning; or a message orcommand (a combined command) to cover both options, i.e., activatecooperative positioning and abandon infrastructure based positioning.

In some embodiments, the detecting operation of Block 606 comprisesdetecting one or more other wireless devices 22 in the service area 18that are at least capable of D2D communications. Of course, the wirelessdevice 22 may constrain or refine its detecting operations using furtherinformation received from the network 10, e.g., limiting its detectionto those other wireless devices 22 that were identified as candidatesfor cooperative positioning operation, based on having D2Dcommunications capability and further having operational configurationsthat permitted their operation in the cooperative positioning mode.

For example, in revisiting FIG. 4, it may be that all user equipments(UEs) in a 3GPP network that are capable of and willing to participatein D2D based cooperative positioning groups, register at some NWE 82. Asnoted, the NWE 82 can be a radio node such as an eNB (in the case ofactive or connected mode UEs), or it can be a core network entity suchas a Mobility Management Entity or MME, to allow the registration ofidle mode UEs by using non access stratum (NAS) signaling for thepurpose of registration.

The NWE 82 can also be a positioning node e.g. an E-SMLC supportingpositioning in an LTE-based network. In this case, a given UE signalsits capability information to the E-SMLC via the LTE PositioningProtocol. Alternatively, the positioning node can acquire the UEcapability related to the cooperative positioning and/or the willingnessto participate in D2D-based cooperative positioning groups from anothernode, e.g., an MME, a radio node, etc. The registration includes theidentity of the UE (e.g. MSISDN), data about the UE's D2D capabilities,its Radio Access Technology (RAT) and frequency band capabilities,positioning capabilities and current navigational satellite accesssituation (e.g. current GPS signal strength/quality).

In turn, the NWE 82 maintains and continuously updates a database (DB)of UEs currently in the cell/registration/tracking area (TA) that areD2D capable. Here, the cell/registration/tracking area is an example ofthe earlier discussed service areas 18 and the database 38 introduced inFIG. 2 may be structured and maintained according to this example. Inparticular, the database 38 may contain information that is registeredby the UEs themselves or that is fetched by the NWE 82 based onsubscription data, which may be obtained based on MSISDNs of the UEs.Such information may indicate the location/positioning capabilities ofsuch UEs, such as their GNSS/GPS capability, their support for E-CID orOTDOA based positioning, etc., along with possibly indicating supportedRATs, frequencies, etc. The NWE 82 may then determine which UEs arecandidates for performing cooperative positioning based on thisinformation and/or may determine the particular cooperative positioningalgorithm(s) to be used by such UEs.

In a further example of contemplated operation, the NWE 82 informs a UE,e.g., upon successful registration of the UE, about the other registeredUEs that are candidates for cooperative positioning. The UE may beinformed using any suitable protocol, e.g., via Radio Resource Control(RRC) signaling in the case of a connected-mode UE, or via NAS signalingin the case of an idle-mode UE, or by using the LTE Positioning Protocol(LPP) in the case that the NWE 82 is an E-SMLC.

Such signaling also may inform the UE about the cellular networkresources (e.g. OFDM resource blocks) reserved for the exchange of datafor the purpose of cooperative positioning, preferred RATs to use forfuture D2D communications, and other parameters that help the UEs tobuild up D2D links. Examples of other such parameters include thetransmission power to use, the modulation and coding schemes to be used,etc. The NWE 82 also may track the current locations of the UEs andsends them valid information to assist cooperative positioning. Forexample, if a UE moves to a new location within the network, the NWE 82sends information to that UE regarding the other UEs in that same areathat are candidates for cooperative positioning.

In such a case, the NWE 82 (or another, cooperating NWE in the new area)may instruct the UE to disregard previous database information sent toit regarding candidate UEs. In general, it will be understood that thedatabase 38 will correspond to a given service area 18 (or areas), andthat it will be dynamically updated as UEs enter and exit the servicearea 18. Such updates may be transmitted to UEs within the service area18 on an as-needed or periodic basis. Of course, one NWE 82 may maintaindatabase information for multiple service areas 18, and arrange for theeNBs in each service area 18 to transmit the cooperative positioningdatabase information applicable to that area.

In another example, the NWE 82 may configure each candidate UE with aduration (e.g., a timer value) up to which the recently sent databaseinformation for cooperative positioning remains valid. This duration mayalso be pre-defined, e.g. as a 10 minute timer. The NWE 82 also mayconfigure candidate UEs with location information (e.g., geographiccoordinate information) for the service area 18 corresponding to themost recently sent cooperative positioning database information. Inturn, the UE may be configured to discard or ignore the databaseinformation if it detects or is told that it has moved out of the areain which such information applies. This location-based discarding may becombined with or complement the time-based discarding, in the interestof preventing the UE from using stale or inapplicable information.

As for the NWE 82 obtaining warning situation information, the NWE 82 inone or more embodiments uses existing technology to determine, senseand/or predict a disaster or public safety situation, and/or level ofwarning situation severity, possibly along with other information, suchas earthquake level, location of earthquake, urgency, measuredtemperature and other sensor data. In particular examples, the NWE 82obtains warning situation information from an ETWS or CMAC server, whichmay communicatively couple to the CN 14 introduced in FIG. 1 via anexternal network or via a private connection into the CN 14.

The NWE 82 may also determine or estimate the portions of networkinfrastructure that are affected by the disaster, or that are expectedto be affected by the disaster. For example, the network containspre-determined information about the location of different networknodes, their coverage areas, their robustness levels or reliabilitylevels in terms of withstanding a disaster, etc., for different regionsof the network. Certain infrastructure nodes may be capable of operatingwithout any disruption or with partial disruption under floods, forexample, whereas some other infrastructure nodes may be capable ofoperating without any disruption or with partial disruption under anearthquake and/or tsunami. The ability of certain network nodes towithstand a particular disaster also depends upon the level and/orduration of the disaster. Therefore, the NWE 82 may use any detailedinformation provided as part of warning situation information toestimate the involved portions of the network.

Complementing such operation, the NWE 82 also determines which UEs inthe affected regions are D2D capable and/or which ones are permitted tooperate in the cooperative positioning mode. Of course, such adetermination may be done as a general step and in advance of detectinga warning situation and determining the affected network areas. The NWE82 in any case may be configured to maintain a list of D2D UEs that arewithin an affected area—i.e., an area of known or expectedinfrastructure impairment—and to take action to insure that these D2DUEs activate cooperative positioning operations, to ensure continued,reliable positioning determinations.

In an example case, the NWE 82 reserves certain cellular resources in agiven service area 18 and instructs the UEs in that area that arecandidates for cooperative positioning to activate cooperativepositioning, in response to determining that the service area 18 isimpaired by a warning situation, or is expected to be impaired. In turn,these candidate UEs begin broadcasting beacon signals in whichpositioning capability information is encoded. Each such candidate UEtherefore looks for the positioning beacon signals from neighboringcandidate UEs, at least within the cellular resources known to bereserved for such usage.

In an example case, the NWE 82 takes such action only if the determinedcriticality level of a warning situation is above a threshold (e.g.severe). However, regardless of whether the NWE 82 uses severity levels,it may modify certain operations in the affected service areas oncecooperative positioning is activated. For example, the NWE 82 mayinstruct the candidate UEs to switch to cooperative positioning methodand stop using infrastructure based positioning for determining theirposition. Further, at least in cases where the NWE 82 is a positioningnode, it may stop providing positioning assistance information (e.g.,cease providing OTDOA assistance information, etc.) at least for thecandidate UEs.

If the NWE 82 is a radio node, then it may stop providing any assistanceinformation for infrastructure based positioning. In addition, it mayalso request that any associated positioning nodes stop providingassistance information for infrastructure based positioning, at least tothe candidate UEs. Alternatively, a radio node operating as the NWE 82may provide the information related to the affected D2D UEs and/orrelated to the obtained public safety situation. In both cases, thepositioning node may stop providing assistance information forinfrastructure based positioning to such UEs. Further, if a givencandidate UE was using infrastructure based positioning before theactivation of cooperative positioning mode, then the NWE 82 mayexplicitly instruct the UE to abandon infrastructure based positioningoperations.

Still further, if the NWE 82 receives any UE positioning measurementresults related to infrastructure based positioning methods and/orreceives UE location information that was determined by anyinfrastructure based positioning method, then the NWE 82 may considersuch positioning information as being unreliable as a consequence of thewarning situation. As such, the NWE 82 may discard such positioninginformation, or it may use such information provided that thepositioning determination is consistent with that obtained throughcooperative positioning methods.

In cases where the NWE 82 uses or is aware of the criticality level of agiven warning situation, it may send only an indication of the warninglevel and rely on the interpretation of that warning level indicator atthe candidate UEs for the selective activation of cooperativepositioning. For example, the NWE 82 sends the criticality level of thewarning situation to the candidate UEs, e.g., pre-determined identifiersare sent, such as no warning=0, mild=1, severe=2, very severe=3.

In another embodiment, the NWE 82 sends the criticality level of thewarning situation as above and also sends additional informationassociated with the warning situation. Examples of the additionalassociated information include: the type of warning (e.g. flood,hurricane, ETWS, etc.; the affected area in terms of geographiccoordinates; the affected network nodes (e.g. cell identifiers such asPhysical Cell Identity or PCI, Cell Global Identifier or CGI, etc.; thetypes of affected nodes, e.g., positioning server, eNBs (or basestations 20, more generally), CN nodes, relays, LMUs and otherpositioning-related nodes; timing related to the warning, e.g., astarting time, end time, event duration, etc. Note that such timinginformation can be given with respect to a reference time, e.g., a GNSSclock, the serving cell timing, an absolute timing, the time in aparticular zone, e.g., Central European Time (CET), etc.

The NWE 82 may cease providing positioning assistance information forinfrastructure based positioning by the affected candidate UEs, at leastuntil the warning severity falls below a predetermined level. Of course,the NWE 82 also may inform the UEs when the warning level returns to anormal level or becomes less severe. In these and other cases, thesignaling from the NWE 82 can be sent to specific UEs, e.g., usingdedicated or group messages, or simply may be broadcast in a generalsense.

The NWE 82 also may inform other network nodes (e.g. neighboring eNBs,positioning nodes, etc.) that certain UEs have been informed about thewarning situation and additional information associated with the warningsituation. The other network nodes may use this received information forseveral purposes. For example if any of them starts serving one of suchUEs, then the new network node can avoid sending the same warningsituation to that UE. In another example, if any of the other networknodes starts serving any such UE and the warning situation changes, thenthe new serving node can send the updated information about the warningsituation to the UE.

As for UE-taken actions, in at least one example configuration, a UE isconfigured to autonomously activate cooperative positioning mode, inresponse to receiving a message from the NWE 82—e.g., the UE may beconfigured to stop using infrastructure based positioning and to beginusing cooperative positioning in response to receiving a warningsituation indication or command from the NWE 82. The UE may be requiredto switch to the cooperative positioning method within a pre-definedtime period, timed from the moment it receives the message containingthe warning related information or within a time T0 (e.g., 500 ms) fromthe start of the warning situation.

The autonomous decision to switch between positioning methods can bebased on pre-determined rule(s). In an example configuration, a UE isconfigured to follow the rule that it shall use cooperative positioningif the warning situation criticality level is above a threshold and/orif the warning is of certain type e.g. earthquake, etc. The UE also maybe configured to inform the network that it has switched to thecooperative positioning mode for determining its location. The UE alsomay forward the information about the warning situation to othercandidate UEs and, in turn, these other candidate UEs may use thereceived information for deciding whether to use cooperative positioningor infrastructure based positioning (or neither mode), depending uponthe severity level of the warning situation.

Of course, UEs also may be configured to detect warning situationswithout receiving information from the network. In such configurations,a UE that can perform cooperative positioning autonomously obtainsinformation related to the criticality level of the warning situationand based on this obtained information it autonomously switches tocooperative positioning. However, the NWE 82 may have pre-configured theUE with information that assists the UE in switching to cooperativepositioning. For example, the NWE 82 may provide the candidate databaseinformation discussed earlier, to aid in the discovery of othercandidate UEs after activation of the cooperative positioning mode.

In an example case, a given UE detects a warning situation based on userinput, or based on monitoring radio, TV, Emergency Broadcast System(EBS) signals, or other such monitoring. In another example, the UE mayinclude or be associated with one or more sensors (e.g., seismic, smoke,etc.) that enable detection of at least some types of warningsituations. In another example, the UE assumes that a warning situationexits based upon its detection of a full or partial loss in networkfunctionality—e.g., the detection of downlink signal disruptions in agiven number of network cells. In yet another example, the UE assumesthat a warning situation applies in response to detecting excessiveerrors in infrastructure based positioning results.

However, in embodiments that use a more “network aware” approach, the UEmay be provided with richer information. For example, the NWE 82 (ormultiple NWEs 82 cooperating together) may transmit signaling thatindicates the particular areas of the network in which cooperativepositioning should be used, and may indicate other areas whereinfrastructure based positioning should be used, or where suchpositioning is at least available and reliable. The NWE(s) 82 also maysend signaling that identifies specific nodes within the network thatare affected by actual or expected impairment. In such cases, a UE maynot activate cooperative positioning unless it determines that itscurrent mode of positioning involves an affected node.

Notably, modifications and other embodiments of the disclosedinvention(s) will come to mind to one skilled in the art having thebenefit of the teachings presented in the foregoing descriptions and theassociated drawings. Therefore, it is to be understood that theinvention(s) is/are not to be limited to the specific embodimentsdisclosed and that modifications and other embodiments are intended tobe included within the scope of this disclosure. Although specific termsmay be employed herein, they are used in a generic and descriptive senseonly and not for purposes of limitation.

What is claimed is:
 1. A method in a network node configured foroperation in a wireless communication network, said method comprising:detecting a warning situation that is associated with actual or expectedimpaired operation of the wireless communication network, at leastwithin a service area; identifying wireless devices in the service areathat are candidates for operating in a cooperative positioning mode forperforming device positioning, wherein the cooperative positioning moderelies on exchanging positioning information between respective wirelessdevices using device-to-device, D2D, communications; and sending amessage to the identified wireless devices, to activate the cooperativepositioning mode.
 2. The method of claim 1, wherein sending the messagecomprises sending a warning situation indicator to the identifiedwireless devices, and wherein the identified wireless devices areconfigured to autonomously activate the cooperative positioning moderesponsive to receiving the warning situation indicator.
 3. The methodof claim 1, wherein sending the message comprises sending an explicitcommand to the identified wireless devices, commanding the identifiedwireless devices to activate the cooperative positioning mode.
 4. Themethod of claim 1, wherein identifying the wireless devices in theservice area that are candidates for operating in the cooperativepositioning mode comprises determining which wireless devices in theservice area at least have D2D communications capability.
 5. The methodof claim 1, wherein identifying the wireless devices in the service areathat are candidates for operating in the cooperative positioning modecomprises determining which wireless devices at least have cooperativepositioning capability.
 6. The method of claim 1, wherein identifyingthe wireless devices in the service area that are candidates foroperating in the cooperative positioning mode further comprisesdetermining which wireless devices are permitted or willing to operatein the cooperative positioning mode.
 7. The method of claim 1, whereinidentifying the wireless devices in the service area that are candidatesfor operating in the cooperative positioning mode comprises receivingcapability information and/or operational configuration information forindividual ones of the wireless devices in the service area.
 8. Themethod of claim 1, wherein the wireless communication network uses radioresources for communicating with wireless devices, and furthercomprising reserving a portion of the radio resources for use incooperative positioning using D2D communications.
 9. The method of claim8, further comprising indicating the reserved portion of the radioresources to the identified wireless devices, either in advance of or inconjunction with sending the message.
 10. The method of claim 1, whereinsending the message comprises sending a warning situation severityindicator, thereby enabling the identified wireless devices to decidewhether or not to activate the cooperative positioning mode independence on the severity of the warning situation as indicated by thewarning situation severity indicator.
 11. The method of claim 1, whereinsending the message further comprises sending any of a warning situationindicator, a warning situation severity indicator, or an explicitcommand to the identified wireless devices, commanding the identifiedwireless devices to abandon use of, or otherwise not use, infrastructurebased positioning operations.
 12. The method of claim 1, wherein sendingthe message comprises sending a mode switching command to the identifiedwireless devices, commanding the identified wireless devices to switchfrom the infrastructure positioning mode to the cooperative positioningmode in response to the mode switching command.
 13. The method of claim1, further comprising sending signaling indicating the identifiedwireless devices, for use by individual ones of the identified wirelessdevices in discovering other ones of the identified wireless devices,for engaging in cooperative positioning.
 14. A network node configuredfor operation in a wireless communication network and comprising: acommunication interface configured for sending signals to wirelessdevices and receiving signals from wireless devices; and a processingcircuit that is operatively associated with the communication interfaceand is configured to: detect a warning situation that is associated withactual or expected impaired operation of the wireless communicationnetwork within a service area; identify wireless devices in the servicearea that are candidates for operating in a cooperative positioning modefor performing device positioning, wherein the cooperative positioningmode relies on exchanging positioning information between respectivewireless devices using device-to-device, D2D, communications; and send amessage to the identified wireless devices, to activate the cooperativepositioning mode.
 15. The network node of claim 14, wherein the networknode comprises a radio base station configured to provide radio servicewithin the service area, the communication interface comprises radiotransceiver circuitry configured to transmit downlink signals to andreceive uplink signals from wireless devices in the service area, andfurther comprises one or more network communication interfaces forcommunicating with other radio base stations and/or with other nodes inthe wireless communication network.
 16. A method in a wireless devicethat is configured for operation in a wireless communication network,said method comprising: detecting a warning situation that is associatedwith actual or expected impaired operation of the wireless communicationnetwork within a current service area of the wireless device; activatinga cooperative positioning mode that relies on exchanging positioninginformation with other wireless devices using device-to-device, D2D,communications; detecting one or more other wireless devices in theservice area that are candidates for engaging in cooperative positioningwith the wireless device; and performing cooperative positioning inconjunction with one or more of the detected wireless devices.
 17. Themethod of claim 16, further comprising receiving information from thewireless communication network that identifies the candidate wirelessdevices, and wherein said step of detecting comprises using the receivedinformation for discovering or otherwise identifying one or more of thecandidate wireless devices.
 18. The method of claim 16, furthercomprising sending information to the wireless communication networkthat indicates that the wireless device is a candidate for operating inthe cooperative positioning mode.
 19. The method of claim 18, whereinsending information to the wireless communication network that indicatesthat the wireless device is a candidate for operating in the cooperativepositioning mode comprises at least one of: sending informationindicating that the wireless device is at least capable of using D2Dcommunications; sending information indicating that the wireless deviceis at least capable of supporting cooperative positioning; and sendinginformation indicating that the wireless device is permitted or willingto perform cooperative positioning.
 20. The method of claim 16, whereindetecting the warning situation comprises receiving a message from thewireless communication network that includes a warning situationindicator, and wherein activating the cooperative positioning modecomprises autonomously activating the cooperative positioning mode inresponse to the warning situation indicator.
 21. The method of claim 16,wherein detecting the warning situation comprises receiving a messagefrom the wireless communication network that includes a command toactivate the cooperative positioning mode, and wherein activating thecooperative positioning mode comprises activating the cooperativepositioning mode in response to the command.
 22. The method of claim 16,wherein detecting the warning situation comprises receiving a modeswitching command from the wireless communication network and switchingfrom the infrastructure positioning mode to the cooperative positioningmode in response to the mode switching command.
 23. The method of claim16, wherein detecting one or more other wireless devices in the servicearea that are candidates for engaging in cooperative positioning withthe wireless device comprises detecting one or more other wirelessdevices in the service area that are at least capable of D2Dcommunications.
 24. A wireless device that is configured for operationin a wireless communication network, said wireless device comprising: acommunication interface for sending signaling to and receiving signalingfrom the wireless communication network; and a processing circuit thatis operatively associated with the communication interface and isconfigured to: detect a warning situation that is associated with actualor expected impaired operation of the wireless communication networkwithin a current service area of the wireless device; activate acooperative positioning mode that relies on exchanging positioninginformation with other wireless devices using device-to-device, D2D,communications; detect one or more other wireless devices in the servicearea that are candidates for engaging in cooperative positioning withthe wireless device; and perform cooperative positioning in conjunctionwith one or more of the detected wireless devices.
 25. A non-transitorycomputer readable storage medium storing a computer program productcomprising computer program instructions that, when executed by aprocessing circuit in a network node that is configured for operation ina wireless communication network, causes the network node to: detect awarning situation that is associated with actual or expected impairedoperation of the wireless communication network within a service area;identify wireless devices in the service area that are candidates foroperating in a cooperative positioning mode for performing devicepositioning, wherein the cooperative positioning mode relies onexchanging positioning information between respective wireless devicesusing device-to-device, D2D, communications; and send a message to theidentified wireless devices, to activate the cooperative positioningmode.
 26. A non-transitory computer readable storage medium storing acomputer program product comprising computer program instructions that,when executed by a processing circuit in a wireless device that isconfigured for operation in a wireless communication network, causes thewireless device to: detect a warning situation that is associated withactual or expected impaired operation of the wireless communicationnetwork within a current service area of the wireless device; activate acooperative positioning mode that relies on exchanging positioninginformation with other wireless devices using device-to-device, D2D,communications; detect one or more other wireless devices in the servicearea that are candidates for engaging in cooperative positioning withthe wireless device; and perform cooperative positioning in conjunctionwith one or more of the detected wireless devices.